Uptake of Fluoride from Aqueous Solution on Nano-Sized Hydroxyapatite: Examination of a Fluoridated Surface Layer

详细信息    查看全文

• 作者：Vanessa Sternitzke ; Ralf Kaegi ; Jean-Nicolas Audinot ; Erik Lewin ; Janet G. Hering ; C. Annette Johnson
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：January 17, 2012
• 年：2012
• 卷：46
• 期：2
• 页码：802-809
• 全文大小：328K
• 年卷期：v.46,no.2(January 17, 2012)
• ISSN：1520-5851

文摘

Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP), both as a synthetic material and as a constituent of bone char, can serve as an effective and relatively inexpensive filter material for fluoride (F^{鈥?/sup>) removal from drinking water in low-income countries. Fluoride uptake on HAP can occur through different mechanisms, which are, in principle, influenced by solution composition. Suspensions of HAP (2 g L鈥?) were equilibrated under controlled pH conditions (pH 6.5, 7.3, 9.5) at 25 掳C for 28 d after the addition of different F鈥?/sup> concentrations (0.5鈥?.0 mM). The reacted HAP solids were examined with Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Nano Secondary Ion Mass Spectroscopy (NanoSIMS). Fluoride uptake on HAP was dependent on pH, with the highest capacity at pH 6.5; the lowest uptake was found at pH 9.5. Under all experimental conditions, the thermodynamically stable mineral phase was fluorapatite, (Ca₁₀(PO₄)₆F₂, FAP). Fluoride uptake capacity was quantified on the basis of FTIR and XPS analysis, which was consistent with F鈥?/sup> uptake from solution. The results of XPS and NanoSIMS analyses indicate that a fluoridated surface layer with a thickness of several nanometers is formed on nanosized HAP.}